When Things Heat Up:
Why Temperature Changes Push on Your Enclosure
Ever left a sealed water bottle in a hot car and heard it creak? The same thing happens to your electronics enclosure. A sealed unit traps air inside and when temperature changes, that trapped air pushes back. Here’s the simple physics behind it.
The Basics (Ideal Gas Law in Plain Clothes)
- Inside your enclosure: PV = nRT. Since the amount of gas (n) and volume (V) are fixed, pressure (P) only dances with temperature (T).
- Translation: when temperature rises, pressure rises; when it cools, pressure falls.
Quick Example
- At room temp (20 °C = 293 K), the pressure inside matches outside: ~1 bar.
- Heat it up to 60 °C (333 K), the ratio is 333/293 ≈ 1.14.
- That’s a 14% pressure increase — so now it’s ~1.14 bar inside.
- Flip it: if cooled to –20 °C (253 K), the ratio is 253/293 ≈ 0.86.
- That’s a 14% pressure drop — so it’s ~0.86 bar inside (a vacuum effect compared to outside).
Why This Matters
- Expansion Stress: Higher pressure stretches seals and gaskets; over time, they can fatigue or leak.
- Vacuum Effect: Cooling pulls outside air, dust, or moisture into any weak point.
- Breathing Enclosures: Cycling between hot and cold makes the unit “breathe,” stressing joints and risking condensation.
The Vent Solution
A vent acts like a pressure “equalizer.” It’s a tiny, engineered pathway that lets air molecules move in and out to balance the enclosure pressure, while blocking the nasty stuff you don’t want inside:
- Waterproof membranes let air pass but stop rain and splashes.
- Dust-tight layers keep fine particles from sneaking in.
- Breathable design prevents condensation by allowing moisture vapor to escape.
In short, vents give your enclosure the ability to breathe freely without compromising protection — keeping electronics safe, dry, and reliable.
Prepared by: Richard Redding – Selectronix Onboard Ltd 18th Sept 2025